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Energy Efficiency of LEDs

Energy efficiency of light sources is typically measured in lumens per watt (lm/W), meaning the amount of light produced for each watt of electricity consumed by the light source. This is known as luminous efficacy

Currently available LED drivers are typically about 85% efficient. Therefore, LED efficacy should be discounted by 15% to account for the driver. For a rough comparison, the range of luminous efficacies for traditional and LED sources, including ballast and driver losses as applicable, are shown below.

Light Source  

Typical Luminous Efficacy Range in lm/W
(varies depending on wattage and lamp type)

Incandescent (no ballast)   

10-18 

Halogen (no ballast)  

15-20 

Compact fluorescent (CFL) (incl. ballast)

35-60 

Linear fluorescent (incl. ballast) 

50-100 

Metal halide (incl. ballast) 

50-90 

Cool white LED 5000K (incl. driver)

47-64*

Warm white LED 3300K (incl. driver)   

25-44*  

Source: DOE as of October 2007